The present invention relates to surgical apparatus and methods in general, and more particularly to apparatus and methods for fixing a ligament in a bone tunnel.
The use of interference screws to fix the ends of a bone-tendon-bone complex to the walls of bone tunnels is well known in the art. It is generally accepted that an interference screw provides sufficient fixation of a bone block in a bone tunnel to allow for early rehabilitation after ligament surgery, such as in anterior cruciate ligament (ACL) reconstruction surgery.
Some techniques avoid using a bone block to fix a ligament in a bone tunnel. Referring to FIG. 1, one such technique involves suspending a ligament L in a bone tunnel C with a pull-through suture S. Over time, the ligament L and surrounding bone grow together, fixing the ligament L in place.
Note: As used herein, the term xe2x80x9cligament Lxe2x80x9d is meant to refer to the replacement ligament being fixed in a bone tunnel. To that end, the replacement ligament L might comprise:
1. ligament or tendon or other tissue harvested from the patient""s own tissue (known as autograft tissue); or
2. ligament or tendon or other tissue harvested from another human donor (known as allograft tissue); or
3. ligament or tendon or other tissue harvested from an animal source (know as xenograft tissue); or
4. ligament or tendon or other tissue made by tissue engineering; or
5. prosthetic ligament made of artificial material; or
6. a combination of the above.
Referring to FIG. 2, another technique uses an interference screw to directly fix ligaments without a bone block (such as a semitendonosis and gracilis tendons) to the walls of the bone tunnel. In this case, the ligament L may be towed into place with suture S, which normally is removed after interference screw fixation has been achieved. However, one disadvantage of direct fixation of the ligament in a bone tunnel with an interference screw is the risk of slippage of the ligament under load prior to the ligament healing to the bone. Such slippage may occur during the rehabilitative period when the ligament is subjected to repetitive loading. To provide for a sufficient interference fit, a large interference screw may be required. However, these large interference screws may cause necrosis of the tendon because of excessive compression of the ligament against the bony tunnel wall.
One object of the present invention is to provide an improved apparatus and method to augment the interference screw fixation of a ligament in a bone tunnel.
Another object of the present invention is to provide an improved apparatus and method to resist slippage of the ligament in a bone tunnel under cyclic loading.
Yet another object of the present invention is to provide an improved apparatus and method for fixing a ligament in a bone tunnel without excessive sideways pressure on the ligament that may result in tissue necrosis.
The present invention provides a jamming retainer to augment the interference screw fixation of a ligament in a bone tunnel, whereby resistance to slippage of the ligament under static and cyclic loading is improved. The invention also provides a jamming retainer for fixing a ligament in a bone tunnel without excessive sideways pressure on the ligament that may result in tissue necrosis. The jamming retainer includes a substantially rigid body with a bore or loop for attaching a ligament or tendon to the jamming retainer. The jamming retainer has a bore or ring for receiving a suture for towing the jamming retainer and ligament or tendon through a bone tunnel. Once the jamming retainer and ligament have been positioned within the bone tunnel, e.g., by towing, the ligament is fixed by insertion of an interference screw to compress the ligament sideways against the wall of the bone canal. However, as noted above, fixation achieved solely by engagement of the interference screw against the ligament is sometimes inadequate; however, with the present invention, this fixation is significantly improved through the use of the jamming retainer in one of two ways. In the first mode, sometimes hereinafter referred to as the xe2x80x9cblocking modexe2x80x9d, the interference screw is advanced into the bone tunnel so as to be just touching, or just short of touching, the jamming retainer. Any subsequent proximal slippage of the ligament will draw the jamming retainer against the distal tip of the interference screw. Further slippage of the ligament is then prohibited by the jamming retainer abutting against the interference screw. In the second mode, sometimes hereinafter referred to as the xe2x80x9csideways compression modexe2x80x9d, the interference screw is advanced until the interference screw engages the jamming retainer and pushes the jamming retainer sideways, thus causing the jamming retainer to be partially embedded in the wall of the bone tunnel. Thus, the jamming retainer is fixed in position by its engagement with the interference screw and the wall of the bony tunnel.